In order to drive steel pipes into the ground a conical impact tip of a rammer engages directly or via a rammer extension or connecting piece in the rear end of a pipe called a following thrust pipe. From DE-OS 33 26 246 a connecting piece is known which is provided with an outer cone engaging in the rear end of a pipe guided on bearing blocks, and concentrically with an inner cone to receive the impact tip of the rammer. Between the outer cone and the inner cone of the connecting piece there are outlet openings for the earth collecting in the inside of the pipe as ramming proceeds.
It has been found that owing to the cone-connection between the rammer and the pipe, the rear end of the thrust pipe is often expanded over the cone to form a flange. This has the disadvantage that the flanged-out end of the pipe must be cut off before the next pipe can be welded on flush with the rear end of the thrust pipe which has been driven in the ground. The flanged pipe ends are usually cut off with a flame-cutting machine. Owing to the restricted space in an excavation the flanged pipe ends cannot, however, be cut off accurately enough, with the result that gaps are often formed between the rear end of the thrust pipe that has already been driven in and the front end of the pipe to be connected to it. Since the thrust of the rammer is transmitted through the weld seam connecting the two pipes into the thrust pipe already in the ground, such gaps must be bridged completely by the weld deposit, which presents great problems in the excavation.